1. Field of the Invention
The present invention relates to an image pickup device, and particularly to an image pickup device having a mask function, and an image processing method therefor.
2. Description of the Related Art
There has been proposed an image pickup device such as a video camera device which has a mask function of outputting a pickup image with keeping a part of the image invisible (hidden). For example, JP-A-2001-69494 discloses a monitoring camera device which can display an image with masking a privacy zone at a part of the image. In this type of monitoring camera device as described above, for example when a monitoring target area contains not only monitoring target objects, but also other target objects such as private houses for which privacy protection is needed, the compatibility between the monitoring function and the privacy protection is established by masking only the target objects for which privacy protection is needed.
According to the conventional image pickup device described above, the video signal of a mask target area (mask area) is also input to automatic exposure (AE: auto exposure) and white balance (WB: white balance/auto-white balance) detection circuits for carrying out image processing to adjust image quality. Therefore, it has had such a problem that the detection results of the detection circuits are changed by image information such as brightness level, brightness variation, etc. of a mask area which is not viewable as an image, so that the overall image picked up by the image pickup device is affected by the image information of the mask area.
For example, when a private house is located in a mask area, if the house is lighted up, the average brightness level of the overall image increases due to the image information of the mask area, and thus such a control operation as to lower the average brightness level is carried out by using the AE function. Therefore, there occurs such a problem that the overall image is darkened on an output video picture even when the brightness levels of image pickup targets other than the masked private house are not varied.